Gas cushion and method and apparatus for its manufacture

ABSTRACT

An inflatable air cushion for use as a safety device in an automobile is made of two blanks cut from strips of fabric interwoven with one another along a seam extending along the peripheries of the blanks. The strips are initially flat, but include at least two side regions spaced from and on opposite sides of the central axis of the resulting cushion and running parallel to either the weft or warp threads of the fabric. These side regions are shrinkable under the influence of heat to a greater degree than a region lying between them to give each blank a convex shape and giving the cushion a more desirable rounded shape when inflated than if made with flat blanks. The ability to form the blanks into convex shapes by heat shrinking avoids the need for employing other more complicated and time consuming shaping procedures.

The invention comprises a gas cushion, in particular for the safetysystem of vehicles, as well as a method for its manufacture and anapparatus for accomplishing the method.

From the German Patent DE-OS 21 21 793 a gas cushion is already known aswell as a method and device for its manufacture. The gas cushion somanufactured is relatively flat and insofar as a safety system of avehicle is concerned it is not adequate.

On the other hand it is known to manufacture gas cushions for safetysystems of vehicles, so-called air bags, which however result inrelatively complicated blanks and stitching work in order to achieve theconvex shape necessary for such air bags.

It is an object of the present invention to form a gas cushion that canbe manufactured in a simple manner without complicated blanks andstitching and to specify as well a corresponding method and a device forits manufacture.

The object according to the present invention is achieved:

(a) through a gas cushion having two overlying fabric blanks which arejoined with one another along their periphery by a stitch seam;

(b) the method for manufacture of the gas cushion in which two fabricstrips are positioned in overlying relationship and are joined togetheralong a predetermined stitch seam to form a cushion-shaped section byshrinking the fabric strips in selected regions; and

(c) an apparatus for manufacturing the gas cushion from two fabricstrips with shrinking of the strips in selected regions.

Advantageous embodiments of the gas cushion are described in furtherdetail below.

Therefore, in a gas cushion whose fabric blanks are joined togetheralong its periphery through a mutual interweaving of seams with oneanother and having shrunken side regions which lie at least in the warpthread direction, a convex, voluminous form is obtained without therequired additional stitch work. Although the shrinkage in the warpthread direction is preferred, it is also possible to have shrinkageexclusively or additionally in the weft direction. The weaving togetherof the fabric strips and the shrinkage of the side regions can beproduced in a continuous process whereby not only a convex gas cushionis produced that is suitable as an air bag for a safety system of avehicle, but also a gas cushion that is manufactured simply, fast andeconomically in few work steps with almost no additional processing. Thegas cushion can consist of a shape that is rectangular or circular inform, or any other desired shape.

It is particularly appropriate if the gas cushion is configured suchthat the transition from the side regions to the center region iscontinuous. Another embodiment is also appropriate whereby in the middleregion of the gas cushion an indentation is produced which is especiallydesirable even for air bags in order to give a person to be saved in avehicle improved lateral support in case of need. One such profiling ofa gas cushion constitutes an improvement by utilizing a reinforcingthread to impart shape to the cushion. In another embodiment theaddition of pleats makes possible a further profiling of the gas cushionif the shrunken side regions should not be adequate for this purpose.

In another embodiment of the gas cushion, the shrinkage in stages at theinterwoven seams, particularly if they are loosely woven there, yieldson the one hand a great firmness and on the other hand high density ofthe seam.

In still a further embodiment the upper, more dense fabric blank holds aperson to be secured more safely in case of need; however the looserweaving of the lower fabric blank permits a certain release of the gasesso that particularly with a sudden inflation of the gas cushion theaccompanying impact is halted and the holding effect of the gas cushionis reduced gradually through escape of gases through the lower fabricblank. This is desirable since the maximum holding force of the gascushion in a safety system of a vehicle is only necessary for the momentof the accident of the vehicle following which, however, the holdingforce should again be reduced in order to be able to set free theprotected person or to set him free.

In still a further embodiment not only the cutting of a gas cushion froma fabric strip is facilitated but also at the same time the threads ofthe fabric of the gas cushion are secured against unravelling.

The method and the apparatus for manufacturing the gas cushion are notparticularly simple, however, as already stated above, they permit avery simple and inexpensive manufacturing of the gas cushion. It is onlynecessary to design the type of strip or select the material of thethreads such that the sections of the side seams of the interwovenfabric strips can be shrunken. The shrinking itself can then be producedin a simple matter through a heating effect whereby the cushion-shapedsection is cut out of the material band along its woven seam.

In one form, the method for manufacturing the gas cushion permits thegas cushion to be further profiled.

In one embodiment, the method for manufacturing the gas cushion utilizesfabric strips made from threads of a thermoplastic synthetic material.Such strips not only make shrinkage more favorable but also permit alater cutting out of the cushion-shaped section by fusion cutting.Moreover by this means the seam is secured. The shrinkage properties ofthe fabric strip permit the method to be varied such that loosely wovensections are shrunk more than the thickly woven sections.

The shrinkage of the cloth strips is accomplished most simply through aprofiled, heated roller since the roller simultaneously contributes tocontrol of the shrinkage. Also, however, infrared and hot air heatingmake possible in particular an additional shrinkage of the fabric stripin which the shrinkage in the weft direction is also possible.

Advantageous gas cushions are obtained through control of the materialsuch that the upper fabric strip is especially dense and the lower clothweb is given a certain gas permeability.

One embodiment of the method introduces reinforcing threads which makepossible a further profiling and stabilization of the gas cushion.

The apparatus suitable for accomplishing the manufacturing method forthe gas cushion comprises a web machine as well as a succeeding devicefor areawise shrinkage of the cloth strip.

One embodiment of the apparatus is especially advantageous in that aprofiled, heated roller controls the shrinkage process especially well.This shrinkage however can also be achieved using infrared or hot airheat alone or in combination with a profiled, heated roller.

The manufactured material strip can be developed practically accordingto one embodiment of the apparatus having a material rack for winding upthe material or the material for example can be directly separated froma strip by means of cutting along a stitch seam of an individual gascushion.

Exemplary embodiments of the object of the invention are furtherdescribed below with the aid of drawings which accordingly illustrate:

FIG. 1 a gas cushion serving as an air bag for a safety system of avehicle as viewed from the front;

FIG. 2 the gas cushion of FIG. 1 in a top plan view;

FIG. 3 a further gas cushion in a view from the front;

FIG. 4 a material strip manufactured in a textile machine with acushion-shaped cutout;

FIG. 5 a heated roller for shrinking the material strip in FIG. 4;

FIG. 6 an apparatus with a heated roller for manufacture of the materialstrip with a gas cushion cutout in schematic illustration;

FIG. 7 a further apparatus with an infrared station in schematicillustration;

FIG. 8. a further apparatus with hot air jets in schematic illustration.

FIG. 9. a first device for fusion cutting as viewed longitudinally; and

FIG. 10. a second device for fusion cutting as viewed longitudinally.

FIGS. 1 and 2 show a gas cushion that can be inserted into a safetysystem of a vehicle. The gas cushion consists of an upper fabric blank 4and a lower fabric blank 6 which are connected with one another throughinterweaving along an inwardly lying seam 8. At the bottom end the seamis interrupted to form an opening 10. The opening 10 serves forinserting an air conduit that is not further illustrated. The gascushion has side regions 12 and 14 oriented in the longitudinaldirection of the warp threads K in which regions the fabric is shrunk.The shrinking decreases towards the center region 16. In the centerregion a further shrunken region 20 is provided at least in the upperfabric blank parallel to the center axis 18. The shrunken side regions12, 14 impart to the gas cushion a convex form. This formation can beadditionally facilitated by means of pleats 22. The shrunken region 20provided along the center axis 18 which likewise can be reinforced bymeans of pleats 24 imparts to the gas cushion an indentation whichserves the purpose, in the event of need, for holding a person to beprotected in the center region of the gas cushion, that is, it preventslateral slipping.

The gas cushion or correspondingly the fabric blanks are manufacturedfrom thread made of a thermoplastic material which makes the shrinkagein predetermined areas possible and the thermal fusion cutting at thestitch seams. At the stitch seam 8 a 1:1 weave is preferably provided.The regions 12, 14 and 20 which are to be shrunk have a looser weavewhich can vary from the outer edge from a 4:4 weave near the stitch seamto a 1:1 weave in the center region. In order to realize the required1:1 weave in each fabric blank, a weaving pattern 1/3/3/1 is necessary,that is, with 1/3, there are 3/4 of the shafts and with that the warpthreads are produced below and the weft threads above in each cloth.With 3/1 there are 3/4 of the shafts, and with that warp threads areproduced above and the weft threads below. It is also possible toprovide the upper fabric blank with higher density and the lower fabricblank with more looseness. The latter will for example achieve asituation in which the lower fabric blank has a thinner weft thread thanthe upper fabric blank exclusively or only in alternating rows and/oreach n-th weft thread is omitted. In this manner the upper, that isfront fabric blank, is thicker than the lower, that is the rear fabricblank, whereby with a sudden inflation of the gas cushion the impact ona person is softened and a gas or particle penetration is prevented.Since the gas cushion in safety systems should only be effective duringthe impact of a vehicle and then its effectivity can attenuate, thelooser weave in the lower fabric blank is of advantage since it makespossible the gradual discharge of air from the gas cushion and with itrelief of the person saved by the gas cushion.

FIG. 3 shows a further gas cushion 2a that corresponds to each of theFIGS. 1 and 2 so that reference should be made to the embodiments above.With the gas cushion 2a however the seam 8a is on the outside so thatthe gas cushion can be manufactured as further detailed below. The upperfabric blank 4a contains an interwoven stronger reinforcing thread 28which is loosely and periodically connected with the lower cloth blank6a and to be sure in such a manner that in the inflated condition theconstrictions 30, 32 are formed at both sides of the gas cushion 2a inthe fabric blanks 4a, 6a, which correspond to the indentations 26 of thegas cushion 2 in FIGS. 1 and 2. Such additional stronger reinforcingthreads 28 also improve the stability of the gas cushion 2a.

FIGS. 4 and 5 reveal the method for manufacturing the gas cushions 2 and2a. In particular FIG. 4 shows a material strip 34 which comes from theweb station of a web machine illustrated in FIG. 6 and from which theupper fabric strip 36 and the lower fabric strip 38 are formed. Thefabric strips 36, 38 are each formed from warp threads K and weftthreads S in a known fashion. At the stitch seam 40 the upper fabricstrip 36 and the lower fabric 38 are tacked together or interwoven sothat a cushion-shaped section 42 is formed in the material strip 34. Theassembling of the threaded materials and/or the weaving of the materialstrips is so selected that a distinct shrinkage behavior results alongthe material strip, particularly transverse to the longitudinaldirection. The center region 44 connects with the two side regions 46₁,46₂, 46₃ with increasing shrinkage characteristics whereby the shrinkagecharacteristics at the outermost areas 46₃ are greatest. Along of thecenter axis 48 the material strip is again provided with a narrow region50 having increased shrinkage characteristics. There, where the fabricstrip should not be shrunk, that is, in the center region 44, a 1:1weaving of the fabric is appropriately provided. The side regions 46₁,46₂, 46₃ and the region 50 at the center axis 48 have on the other handa weave that, for example, can extend from the 2:2 weave at the junctionwith the center region 44 to a 4:4 weave or more at the outer region.The stitch seam is moreover provided with a space 52 at which the fabricstrips 36, 38 are not connected with one another and this serves foraffixing a valve or a gas conduit. The material strip 34 manufactured inthis manner after being drawn off the web machine is guided over aheated roller 54 which has reduced cross-section which preferably areformed through conical sections 56, 58 at the regions to be shrunk. Byguiding the material strip over the heated roller 54 the strip is shrunkat the corresponding regions 46₁, 46₂, 46₃ as well as 50. The shrunkenmaterial strip can then be further processed immediately or can berolled up on a material rack illustrated in FIG. 6. The material rack ispreferably provided likewise with sections of reduced cross-sectionsimilar to the heated roller 54.

The cushion-shaped sections 42 are then cut out of the material strip somanufactured along the stitch seam 40 by means of thermal fusioncutting, if necessary with still additional stitching provided at theshrunken regions. The cushion-shaped sections 42 can then be formeddirectly into the cushion 2a according to FIG. 3 or after being turnedinside out, the cushion 2 according to FIGS. 1 and 2.

FIG. 6 shows in a schematic illustration a lateral view of an apparatuswith a conventional web machine for manufacture of the gas cushions. Thematerial strip shown in FIG. 3 is woven at the web station 60. In orderto achieve the densest fabric possible, the web station 60 is associatedwith a clamping bar holder or a material holddown according to PatentApplication W089/08734 equivalent to U.S. Pat. No. 5,052,447 which isnot illustrated. The latter can be heated in the middle region in orderto preprocess the material strip at that region, that is the middleregion, which should not be shrunk upon itself, in order to eliminateresidual tension. The material strip is guided by means of dischargedevice 62, consisting of the discharge roller 64 with an infeed holddownroller 66 and with a outfeed take-off roller 68, over the heated roller54 which consists of the conical sections 56, 58. Thereafter theshrunken material strip is wound up on the material rack 70 whichlikewise is provided with conical sections 72 corresponding to theheated roller 54.

FIGS. 7 and 8 show two further variations of such an apparatus wherebythe heated roller 54 is supplemented by means of an infrared beamingdevice 74, 76 according to FIG. 7 and hot air jets 78, 80 according toFIG. 8.

FIGS. 9 and 10 show a device for fusion cutting of the material strip tobe manufactured, for example, according to FIGS. 4 to 8. The fusioncutting is produced directly after the shrinkage in series with themanufacture of the material strip or after intervening storage. Theapparatus of FIG. 9 consists of a roller 82 with conical sections 84associated with the shrinkage regions of the material strip. The shaftis provided with a cutting blade 86 shaped in a manner corresponding tothe pattern to be cut from the material strip. The material strip ispressed by means of heated pressure rollers 88 against the blade 86. Theapparatus according to FIG. 10 includes a roller 90 with lateral,conical sections 92 on which the material strip rests. The heatedrollers 94 with continuous cutting blades 96 serve as cutting elementswhich are pressed against the roller 90 and are shifted laterally bymeans of electronic controls according to the pattern to be cut.

Still further embodiments are possible. In particular it is possible toshrink the web exclusively or additionally in the weft direction. Herethe weft threads must on the one hand and the web conditions on theother hand, in particular the density of the warp threads, be soadjusted that a shrinkage is possible in the weft direction. Besides thegas cushion can also be produced transverse to the longitudinaldirection of the material strip, that is transverse to the warpdirection. The shrinkage is then produced over a level cylindricalheated roller.

In the claims which follow, when it is said that a fabric blank or stripis shrunk in one region to a lesser degree than in some other region orregions, such lesser degree of shrinking is intended to include thepossibility of the blank or strip not being shrunk at all in said oneregion while being shrunk to some degree in said other region orregions.

I claim:
 1. A gas cushion, in particular for the safety system of avehicle, having two overlying fabric blanks woven out of a set of weftthreads and a set of warp threads, said blanks having a center axis andbeing joined with one another at their peripheries by means of mutualinterweaving at a seam, said blanks each having at least two sideregions located on opposite sides of and spaced from said center axisand each having at least one center region located between its two sideregions, said side regions extending parallel to the threads of one ofsaid sets of threads, characterized in that each of said fabric blanksis shrunk in its said side regions to a greater degree than in its saidcenter region.
 2. A gas cushion according to claim 1 characterized inthat said center region of each of said blanks runs parallel to its saidside regions, and that the shrinkage in said side regions decreases inmoving towards said center region.
 3. A gas cushion according to claim 1characterized in that at least one of said fabric blanks has a narrowregion lying along said center axis and spaced from its side regions andwhich narrow region of said at least one blank is shrunk to a greaterdegree than is its said center region.
 4. A gas cushion according toclaim 1 characterized in that said gas cushion has a middle regionrunning parallel to and spaced from said side regions of said blanks,and that said gas cushion has reinforcing threads interwoven with saidfabric blanks at said middle region of said cushion and which threadsare periodically connected loosely between said blanks.
 5. A gas cushionaccording to claim 1 characterized in that at least one pleat is locatedin at least one of said side regions of at least one of said blanks. 6.A gas cushion according to claim 1 characterized in that said seam isshrunk at least in the portions thereof located in said side regions ofsaid blanks.
 7. A gas cushion according to claim 1 characterized in thatsaid two fabric blanks consist of an upper fabric blank and a lowerfabric blank, and that said upper fabric blank has a more dense weavethan said lower fabric blank due to said upper fabric blank being madewith weft threads which are individually thinner than the weft threadsof said lower fabric blank.
 8. A gas cushion according to claim 1characterized in that said fabric blanks are ones formed by means ofthermal fusion cutting of said blanks from a strip of material made oftwo overlying strips of interwoven fabric.
 9. A gas cushion according toclaim 1 characterized in that said two fabric blanks consist of an upperfabric blank and a lower fabric blank, and that said upper fabric blankhas a more dense weave than said lower fabric blank due to said lowerfabric blank being made with weft threads which are fewer in number thanthe weft threads of said upper fabric blank.
 10. A method formanufacturing a gas cushion in which a material strip made from twofabric strips of equal width, directly overlying one another andcomposed of weft threads (S) and warp threads (K), is formed in aprocess in which said warp and weft threads of said two fabric stripsare interwoven with one another at a predetermined seam to form acushion shaped section, characterized in that the side regions of saidmaterial strip which extend into said cushion shaped section are firstso made that said side regions will shrink under a warming effect, saidinterwoven fabric strips are then shrunk in said side regions by meansof a warming effect, and finally, said cushion shaped section is cutfrom said material strip along said interwoven seam.
 11. A methodaccording to claim 10 characterized in that at least one of said twofabric strip is made so as to additionally include a narrow regionrunning parallel to and spaced from said side regions and shrinkableunder a warming effect, and in that said narrow region is also shrunk bya warming effect.
 12. A method according to claim 10 characterized inthat said fabric strips are manufactured from a thermoplastic material.13. A method according to claim 10 characterized in that said fabricstrips are woven in said side regions with a looser weave than in therest of said strips.
 14. A method according to claim 10 characterized inthat said fabric strips are shrunk in said side regions by passing themover at least one heated roller having a reduced cross-section along thelength thereof engageable with said side regions of said material strip.15. A method according to claim 10 characterized in that said fabricstrips are shrunk in said side regions by means of indirect heating. 16.A method according to claim 10 characterized in that said fabric stripsconsist of an upper fabric strip and a lower fabric strip, and that saidupper fabric strip is manufactured to be more dense than said lowerfabric strip by using in said upper fabric strip weft threads which areindividually thinner than the weft threads of said lower fabric strip.17. A method according to claim 10 characterized in that said materialstrip has a middle region extending parallel to and spaced from saidside regions, and at least one reinforcing thread is interwoven with oneof said fabric strips and is periodically connected loosely with theother of said fabric strips.
 18. A method according to claim 10characterized in that said fabric strips consist of an upper fabricstrip and a lower fabric strip, and that said upper fabric strip ismanufactured to be more dense than said lower fabric strip by using insaid lower fabric strip weft threads which are fewer in number than theweft threads of said upper fabric strip.
 19. An apparatus formanufacturing a gas cushion comprising: a weaving machine for thecontinuous manufacture of a material strip made up of two fabric stripsoverlying one another and for interweaving said fabric strips along apredetermined seam, each of said strips having a center axis extendingalong the length of the strip, two side regions located on oppositesides of and spaced from said center axis and a center region locatedbetween said two side regions, said side regions and said center regionextending continuously along the length of the strip, said weavingmachine having a discharge station from which said material strip madeby said machine emerges, and a shrinking device associated with saiddischarge station of said weaving machine for continuously receivingsaid material strip as it is discharged from said discharge station andfor continuously shrinking each of said fabric strips of said materialstrip such that each of said fabric strips is shrunk to a greater degreein its said side regions than it is in its said center region, saidshrinking device including a heated roller over which said materialstrip passes, said roller having two side sections over which said sideregions of said fabric strips pass and at least one center section overwhich said center regions of said fabric strips pass, said side sectionsof said heated roller having cross-sections of reduced diameter incomparison to the diameter of the cross-section of said center section.20. An apparatus according to claim 19 characterized in that said devicefor shrinking the fabric strips also includes an infrared beaming devicefor heating said side regions of said fabric strips.
 21. An apparatusaccording to claim 19 characterized in that said device for shrinkingsaid fabric strips also includes hot air jets for heating said sideregions of said fabric strips to be shrunk.
 22. An apparatus accordingto claim 19 characterized in that said apparatus has a material rack forwinding up said material strip, said rack having side sections ofreduced cross-section associated with said side regions of said fabricstrips.
 23. An apparatus according to claim 19 characterized in thatsaid apparatus has a thermal cutting device following said device forshrinking said fabric strips, said thermal cutting device having acutting roller corresponding in shape to said heated roller so as tohave two side sections over which said side regions of said fabricstrips pass and at least one center section over which said centerregion of said fabric strips pass, said side sections of said cuttingroller having cross-sections of reduced diameter in comparison to thediameter of the cross-section of said center section of said cuttingroller, and heated cutting blades associated with said cutting roller.